Hi Andrew,
I modified the Configured Aquisition Example to read more than 1 record, and it was the same, so I start the VI with one channel and it was like 1300ms, I started the VI with two channels and it was like 70 ms, but when I started the VI with two channels and then while running I changed to just one channel it worked well it was the same as the two channels, I don't know why.